1. Technical Field
The disclosure relates to backlight driving systems, and particularly to a multi-lamp driving system.
2. Description of Related Art
Cold cathode fluorescent lamps (CCFL) are usually used for a backlight of a liquid crystal display. An inverter converts direct current power into alternating current power to provide proper driving power to light the CCFLs. The inverter usually utilizes a single sided printed circuit board without a high voltage capacitor in order to reduce costs. In this structure, the inverter does not have voltage feedback. In order to solve the above problem, the inverter first uses frequency hopping and soft starting, and then uses a fixed duty cycle driving mode to light the CCFLs.
The inverter using the fixed duty cycle driving mode uses a decreased duty cycle because of concern of tolerance voltage of transformers and lighting voltage. In poor environment, such as, environments with low temperature, low lamp current, or darkroom, lamp current fluctuates when the CCFLs are driven by the inverter, which results in the CCFLs flickering, mis-acting to protect, or the CCFLs lighting failure.